Brown vetoed that bill on the same day he signed a bill extending HOV-lane access for solo drivers of electric cars, plug-in hybrids and alternative-fuel vehicles, and OK’d other measures to promote the use of “green” vehicles.

The overall message is clear: Brown won’t risk diminishing the incentive for motorists to carpool by letting solo drivers have even limited access to the HOV lanes.

Never mind that bumper-to-bumper traffic can’t be good for the environment.

The Gatto bill would have established a one-year experiment. The plan could have been canceled if was causing problems. Brown owed it to Southern Californians to find out what the effects would have been.